The principal objective of this project is to study the mechanism by which simple neural networks process information with particular emphasis on mechanism of learning. The nervous system of Hermissenda crassicornis has proven to be an excellent model for information processing at several levels: sensory transduction by photoreceptors and hair cell, analysis of synaptic circuitry, changes is synaptic circuitry produced by conditioning paradigms administered to intact animals as well as to isolated nervous systems, membrane properties modified by conditioning, identification of critical developmental stages for the neural networks studied as well as stages critical for learning. Techniques employed thus far to pursue these questions include: simultaneous intracellular recording from multiple neural elements, paired stimulation of the visual and vestibular pathways using a rotating table, iontophoresis of fluorescent dyes. Other methods planned will allow biochemical and genetic approaches to the above problems. These include mariculture, subcellular fractionation protein phosphorylation analysis, and uptake of neurotransmitter precursors.